Diagnostic Test
- READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR DTC TO RETURN WARNING:
On vehicles equipped with the high voltage system, you must thoroughly read and follow all High Voltage Safety procedures. In addition, before performing any diagnostic or service procedure near a high voltage component, you must perform the High Voltage Power Down. Failure to follow these instructions may result in possible serious or fatal injury.
Read the HIGH-VOLTAGE SAFETY PROCEDURES. Refer to HIGH VOLTAGE SAFETY PROCEDURES .
When the HIGH-VOLTAGE POWER-DOWN PROCEDURE is necessary. Refer to VEHICLE HIGH VOLTAGE POWER DOWN .
- With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
- For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
- With the scan tool, erase all DTCs.
- Turn the ignition off for a minimum of 10.0 seconds.
- Turn the ignition on.
- Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
- With the scan tool, read DTCs.
Did the DTC return?
Yes
- Go To 2
No
- Perform the appropriate INTERMITTENT CONDITION diagnostic procedure. Refer to TESTING FOR AN INTERMITTENT CONDITION .
- CHECK FOR LIN BUS DTCS
- Refer to the recorded DTCs.
Are there any LIN Bus DTCs Active?
Yes
- Repair the LIN Bus DTCs first. Refer to DIAGNOSTIC CODE INDEX .
No
- Go To 3
- Refer to the recorded DTCs.
- ISOLATE AND LOAD TEST THE (A870) FUSED B+ CIRCUIT TO CHECK FOR HIGH RESISTANCE
- The ignition must be off when performing a load test on a circuit.
- Isolate the circuit by disconnecting the Electronic Control Unit (ECU) and every component harness connector containing the circuit being tested.
- Connect the positive lead of the load test tool to the positive side of the Battery (A). Note: Refer to the diagram below.
- Using an approved back probe tool, connect the negative lead of the load test tool to the circuit being tested at the one of the component harness connectors (B).
- Using an approved back probe tool and a fused jumper wire, connect the circuit being tested to the negative side of the Battery or a known good ground at the other component harness connector (C and D).
- The bulb on the load test tool should be illuminated and bright if there is no resistance in the circuit.NOTE:
Why load test a circuit? A load test is used to determine if a circuit is capable of carrying the amperage needed to perform properly. The 3156 bulb in the load tool illustrated, is a simple but effective method of testing circuit functionality. A 3156 Bulb has approximately 6.0 Ohms of resistance when the bulb is powered and draws approximately 2.0 amps of current. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .
NOTE:A 12-volt test light can be substituted for the load test tool, but only if the test light draws enough current to effectively load test the circuit. Many high impedance test lights draw very little amperage (less than 0.1 amps) and are not reliable to load test a circuit. To perform a proper load test of a circuit, the tool being used should draw more than approximately 0.75 amps.
NOTE:Why perform a Voltage Drop Test? To verify with certainty there is not any resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. To do so perform the following:
- Connect the leads of a DVOM to the alligator clips on the load test tool while the load test tool is connected in series with the circuit.
- Compare the voltage drop across the bulb to the voltage reading across the Battery terminals.
- The voltage dropped across the bulb should be equal to the voltage reading across the Battery terminals if there is no resistance in the circuit being tested. Refer to VOLTAGE DROP TEST PROCEDURE
WARNING:To avoid possible serious or fatal injury, DO NOT load test any air bag/restraint system components or circuits using the procedures listed here. Refer to the Service Information for proper air bag/restraint system testing procedures.
CAUTION:Do not load test any circuits with components still connected to the circuit.
NOTE:When probing a circuit at an Electronic Control Unit (ECU) harness connector, always use an appropriate back probing tool to prevent any possible damage to the ECU terminals.
NOTE:Compare the brightness of the bulb in the load test tool to that of a direct connection to Battery.
Is the load test bulb illuminated and bright?
Yes
- Go To 4
No
- Repair the circuit for an open, open fuse, or high resistance.
- If the fuse is open, check for a short on the circuit or shorted component on the circuit.
- Perform the Electric Vehicle Control Unit (EVCU) VERIFICATION TEST. Refer to ELECTRIC VEHICLE CONTROL UNIT (EVCU) VERIFICATION TEST .
- CHECK THE (Z909) AND (Z85) GROUND CIRCUIT FOR HIGH RESISTANCE BY LOAD TESTING THE CIRCUIT
- Disconnect the component harness connector to isolate the ground circuit.
- Connect the positive lead of the load test tool to the positive side of the Battery.
- Connect the negative lead of the load test tool to the ground circuit at the component harness connector (A). Note: refer to the diagram below.
- The bulb on the load test tool should be illuminated and bright if there is no resistance in the circuitry.NOTE:
Why load test a circuit? A load test is used to determine if a circuit is capable of carrying the amperage needed to perform properly. The 3156 bulb in the load tool illustrated, is a simple but effective method of testing circuit functionality. A 3156 Bulb has approximately 6.0 Ohms of resistance when the bulb is powered and draws approximately 2.0 amps of current. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .
NOTE:A 12-volt test light can be substituted for the load test tool, but only if the test light draws enough current to effectively load test the circuit. Many high impedance test lights draw very little amperage (less than 0.1 amps) and are not reliable to load test a circuit. To perform a proper load test of a circuit, the tool being used should draw more than approximately 0.75 amps.
NOTE:Why perform a Voltage Drop Test: To verify with certainty there is not any resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. To do so perform the following:
- Connect the leads of a DVOM to the alligator clips on the load test tool while the load test tool is connected in series with the circuit.
- Compare the voltage drop across the bulb to the voltage reading across the Battery terminals.
- The voltage dropped across the bulb should be equal to the voltage reading across the Battery terminals if there is no resistance in the circuit being tested. Refer to VOLTAGE DROP TEST PROCEDURE
NOTE:When probing a circuit at an Electronic Control Unit (ECU) harness connector, always use an appropriate back probing tool to prevent any possible damage to the ECU terminals.
NOTE:Compare the brightness of the bulb in the load test tool to that of a direct connection to Battery.
Is the load test bulb illuminated and bright?
Yes
- Replace the Electric Coolant Heater (ECH) in accordance with the Service Information.
- Perform the Electric Vehicle Control Unit (EVCU) VERIFICATION TEST. Refer to ELECTRIC VEHICLE CONTROL UNIT (EVCU) VERIFICATION TEST .
No
- Repair the ground circuit for an open or high resistance.
- Perform the Electric Vehicle Control Unit (EVCU) VERIFICATION TEST. Refer to ELECTRIC VEHICLE CONTROL UNIT (EVCU) VERIFICATION TEST .